Supramolecular complexation of C60 with branched polyethylene.

Fullerene C60 is a ubiquitous material for application in organic electronics and nanotechnology, due to its desirable optoelectronic properties including good molecular orbital alignment with electron-rich donor materials, as well as high and isotropic charge carrier mobility. However, C60 possesses two limitations that hinder its integration into large-scale devices: (1) poor solubility in common organic solvents leading to expensive device processing, and (2) poor optical absorbance in the visible portion of the spectrum. Covalent functionalization has long been the standard for introducing structural tunability into molecular design, but non-covalent interactions have emerged as an alternative strategy to tailor C60-based materials, offering a versatile and tuneable alternative to novel functional materials and applications. In this work, we report a straightforward non-covalent functionalization of C60 with a branched polyethylene (BPE), which occurs spontaneously in dilute chloroform solution under ambient conditions. A detailed characterization strategy, based on UV-vis spectroscopy and size-exclusion chromatography was performed to verify and investigate the structure of the C60+BPE complex. Among others, our work reveals that the supramolecular complex has an order of magnitude higher molecular weight than its C60 and BPE constituents and points towards oxidation as the driving force behind complexation. The C60+BPE complex also possesses significantly broadened optical absorbance compared to unfunctionalized C60, extending further into the visible portion of the spectrum. This non-covalent approach presents an inexpensive route to address the shortcomings of C60 for electronic applications, situating the C60+BPE complex as a promising candidate for further investigation in organic electronic devices.

Amide-Assisted Polymerization of 1,3-Butadiyne Containing Thiolate Ligands on Small Gold Nanoparticles.

Incorporation of directing amide groups has been shown to facilitate the topochemical polymerization of 1,3-butadiyne (diacetylene) groups in noncrystalline phases such as gels, amorphous solids, and liquid crystals. It remains challenging to polymerize 1,3-butadiyne-containing alkylthiolate ligands within their self-assembled monolayers on gold nanoparticles (AuNPs), which enhances their stability and adds new optical and electronic properties. Especially smaller AuNPs of sizes below 5 nm in diameter have been reported to display sluggish photopolymerization and are susceptible to photodegradation under UV irradiation. To probe the effectiveness of the amide-directed photopolymerization of 1,3-butadiyne ligands, small AuNPs in the 2-4 nm range were synthesized that contain alkylthiolate ligands with and without amide and 1,3-butadiyne groups. Their photopolymerization and photostability were studied by transmission electron microscopy (TEM), UV-vis spectroscopy, and Raman spectroscopy. AuNP with amide-free 1,3-butadiyne ligands templated the polymerization of the 1,3-butadiyne ligands but fused to large and insoluble particles during the polymerization process. AuNPs with ligands containing both 1,3-butadiyne and amide groups polymerized significantly faster, which slowed down photodegradation. A UV irradiation (254 nm and 176 W/m2) for 5-10 min was found to be optimal for the AuNPs with directing amide groups studied here, although their average core sizes grew from 3.8 to 4.0 nm in diameter and about 20% of the attached 1,3-butadiyne ligands remained unreacted after 10 minutes of irradiation. About 75% of the attached 1,3-butadiyne ligands were already polymerized during the first 5 min of UV irradiation. This decrease in reactivity is reasoned with a fast polymerization of ligands attached to facet sites and slower polymerization rates for ligands attached to edge and corner sites. Unexpectedly, photopolymerization occurred only in the presence of solvent, whereas no polydiacetylene was generated when dry powders of any of the diacetylene-containing gold nanoparticles were irradiated.

The biosynthesis of the cannabinoids.

Cannabis has been integral to Eurasian civilization for millennia, but a century of prohibition has limited investigation. With spreading legalization, science is pivoting to study the pharmacopeia of the cannabinoids, and a thorough understanding of their biosynthesis is required to engineer strains with specific cannabinoid profiles. This review surveys the biosynthesis and biochemistry of cannabinoids. The pathways and the enzymes' mechanisms of action are discussed as is the non-enzymatic decarboxylation of the cannabinoic acids. There are still many gaps in our knowledge about the biosynthesis of the cannabinoids, especially for the minor components, and this review highlights the tools and approaches that will be applied to generate an improved understanding and consequent access to these potentially biomedically-relevant materials.

Topochemical Polymerization of a Nematic Tetraazaporphyrin Derivative To Generate Soluble Polydiacetylene Nanowires.

Polydiacetylenes are well-established one-dimensional organic semiconductors that have been generated by photochemical and thermal polymerizations of diacetylenes in single crystals, gel phases, thin films, and membranes. Their formation in mesophases, such as liquid crystals, has been surprisingly little studied although higher-ordered mesophases should support the topochemical polymerization of diacetylenes (1,3-butadiyne groups) and may give access to large domains of uniformly aligned materials. The polymerization of diacetylenes in a mesophase may also increase the stability of the self-assembled supramolecular structure. Here, the dye and discotic mesogen tetraazaporphyrin was decorated with eight diacetylene-containing alkyl chains to probe its mesomorphism and conversion into multifunctional polydiacetylene materials. While the incorporation of diacetylene groups supports columnar mesomorphism, successful photopolymerization required the presence of directing amide groups that suppressed columnar in favor of nematic mesomorphism. Still, the polymerization of the nematic mesophase generated a soluble nematic polydiacetylene of significantly higher molecular weight (Mn = 77 kDa or 25 monomer units by gel permeation chromatography) than what has been obtained in gel phases of related compounds. The formation of polydiacetylene was confirmed by Raman spectroscopy, and its nematic structure was verified by UV-vis spectroscopy, polarized optical microscopy, and X-ray diffraction. Both its nematic structure and the incorporation of eight side chains per discotic unit provide the polydiacetylene with sufficient solubility for casting thin films on substrates. Atomic force microscopy studies of films on silicon wafers revealed a grid-like structure of connected nanofibers. This study demonstrates the requirements for the formation of multifunctional mesomorphic polydiacetylene materials from mesomorphic precursors and their advantages. Optimization of the presented molecular design should give access to other mesophases and, consequently, functional polydiacetylene materials with tunable structures and optoelectronic properties.

Cu0-Loaded organo-montmorillonite with improved affinity towards hydrogen: an insight into matrix-metal and non-contact hydrogen-metal interactions.

Copper-loaded organo-montmorillonite showed improved affinity towards hydrogen under ambient conditions. Clay ion exchange with a propargyl-ended cation followed by thiol-yne coupling with thioglycerol resulted in a porous structure with a 6 fold higher specific surface area, which dramatically decreased after copper incorporation. X-ray diffraction and photoelectron spectrometry, nuclear magnetic resonance (1H and 13C) and CO2-thermal programmed desorption revealed strong sulfur:Cu0 and oxygen:Cu0 interactions. This was explained in terms of structure compaction that 'traps' Cu0 nanoparticles (CuNPs) and reduces their mobility. Transmission electron microscopy showed predominant 1.0-1.5 nm CuNPs. Hydrogen capture appears to involve predominantly physical interaction, since differential scanning calorimetry measurements gave low desorption heat and almost complete gas release between 20 °C and 75 °C. Possible hydrogen condensation within the compacted structure should hinder gas diffusion inside CuNPs and prevent chemisorption. These results allow safe hydrogen storage with easy gas release to be envisaged even at room temperature under vacuum. The reversible capture of hydrogen can be even more attractive when using natural inorganic supports and commercial plant-derived dendrimers judiciously functionalized, even at the expense of porosity.